I would suspect either a bad #4 pressure valve holder seal or a bad #4 injector. You also need to check the compression, you could have a valve problem with #4 (check for lifter noise, this car has hydraulic tappets, too -- if the intake for #4 is completely flat or you have a worn cam, you could have low compression on #4).

You could also have a cracked head, its the same as the other OM603 engines and VERY intolerant of even transient overheating.

Bad injector can be tested by swapping then around -- if the noise follows the injector, it needs rebuilding or replacement.

The blast of hot air after shutting off is characteristic of this car -- the heater valve is held closed by current, so when you switch off the heater core is open. There is enough thermosiphon pressure to circulate hot coolant into the heater core, so it will blow hot until it cools off. The monovalve can also leak, constantly trickling coolant through the core. The AC will catch up eventually.

You should also check the cabin temp sensor blower for operation, but I don't knwo where it is on that model. I believe the sensor is behind the little grille next to the overhead dome light -- see if a small piece of tissue is held up by suction with the engine running and CC on. If not, the blower is not working and cabin temp control will be goofy.

Peter

PSFRED. I took the car to the guy that rebuilt my injectors today so he could listen to the engine as he was here at Lake Powell at his second home (he owns advanced diesel injection in San Diego) and he said that it sounds like I need to have the IP valves balanced. He has a $110K digital machine that can balance the pressure valves ??????? I also did the test to see how fast the car would get to 60 mph from a dead stop and it would get there in 8 seconds every time by me counting 1001, 1002, and so on, and I was at 4500 ft. After that I went out on a six mile straight and spun her up to 128 mph with no problem and it was still pulling. How fast will these machines go, just curious, I do not want to max it out. But, it seems to run a lot better after my power runs. Also how long will the glow plugs stay on after the light goes out before you engage the starter ? I really appreciate your replies, and anyone else for that matter.

Pressure valve balancing? I'd think that only the start of delivery/delivery volume can be adjusted, and it requires pump disassembly to calibrate them.

Uneven fuel delivery shows up as rough idle, not smoke as a general rule.

A leaking delivery valve seal will cause a knock, but usually not smoke.

It sure sounds like bad injector or prechamber to me.....

The performance you have is about normal, top end is around 130 mph. That is one reason I suspect a bad injector or prechamber, they cause much more trouble at low rpm than at high rpm. The affected injector needs to be removed and properly tested for leaks, opening pressure, sticking, and spray pattern.

MB diesels thrive on hard use -- driving them slowly in stop and go traffic will result in sluggish performance, excessive smoke, and knock. A good highway run clears them out.

Glow plugs will run about 90 sec if the key is not turned to the start position before that. On the 350, they stay on 20 sec or so after start.

Peter

Isn't Lake Powell more like Lake Puddle these days?

I've seen a modern IP calibration machine and it's quite a piece of work. I don't think it can be hooked up while the IP is in the car. If you pull the side cover, you'll see a rack that links to each delivery valve. Calibrating is for the most part setting all the delivery valves against the rack. Someone with a golden touch might be able to wing the adjustment in-situ but I expect a person with that skill is off making millions doing something else.

Do you get hot air from the defrost vents in defrost mode with the engine at operating temp? Might be easier to check if you disconnect power to the compressor by pulling one of the wires at the AC dryer low pressure switch behind the left headlight. If not, I'd suspect a bad climate control unit (also the push button unit in your car).

Sixto
95 S420
87 300SDL

Yeah, Lake Powell is gone. We sure miss it as I am in the marine engine repair business. The lake is 540 ft. deep and we are 140 ft down from full pool, but the acre foot volume is a little less than 50 % so the media makes it look like there is nothing here. The upside is the incredible beaches we have now and the fishing is the best in 32 years, so really, it is the best that I have ever seen it ! I am sure the Cal. machine that you are referring to is what he has, and the pump has to be sent to him, but he says that if the cam is good, it will restore the engine to near new nailing free smoothness after the calibration. I bought the PV seals after reading what Peter said and I will replace them first and give you all an update as I will be in a continous project with this engine to get it dialed in to its max performance. You say disconnect the AC comp. switch at the dryer. Are you saying that the AC is coming on ? It is a heater problem like I have never seen as it works great after you restart, but then the temp will not stay hot with the dial at max red. It takes about five minutes on the road for the heat to go to near cold wiith the button on arrow down and the fan on low. ?????

In defrost mode the monovalve should be wide open allowing full heat into the cabin. But the AC compressor is going full tilt as well so it might be difficult to tell if you're getting heat. All we're after here is to determine if the PBU is capable of sending any 'heat' signal to the monovalve so we can delay calling the PBU bad. I think that's what it is but might as well rule out the cabin temp sensor first.

As Peter said, the monovalve opens when you shut off the engine. The hot engine coolant gets to the heater core (how, I don't know) so you get a billow of hot air when you restart. It won't last because there isn't much heat stored in the heater core after the monovalve closes.

Sixto
95 S420
87 300SDL

Why is the AC compressor on the heat mode ? I need to see if the CD Rom service manual that I just received has a coolant flow diagram so I can understand how this system works, and how to test it. I need to find a source for these CD's that will work with Windows XP. The discs I got from someone on ebay will only work on Windows 95-98 with Adobe Acrobat 4.0 !

The compressor is on in defrost mode (not heat mode which is more or less the next button over) for dehumidifying.

Sixto
95 S420
87 300SDL